1. Field of the Invention
The present invention relates to a microfluidic device for electrochemically regulating the pH of a fluid therein and a method of electrochemically regulating the pH of a fluid using the microfluidic device.
2. Description of the Related Art
A microfluidic device is a device in which an inlet, an outlet, a reaction vessel, etc., are connected through microchannels. A microfluidic device also includes a micropump for transporting fluids, a micromixer for mixing fluids, and a microfilter for filtering fluids.
Such a microfluidic device is well known in the art and is used in a microanalysis device such as a lab-on-a-chip (LOC), which performs a series of biological analysis processes including cell enrichment, cell lysis, biomolecular purification, nucleic acid amplification like polymerase chain reaction (PCR), nucleic acid isolation, protein purification, hybridization, and detection. To perform the various biological analysis processes, the microfluidic device requires a different pH in each step. In the biological analysis processes, a conventional method of regulating pH is performed by adding or eliminating an acid solution, an alkaline solution, a neutralization solution, or a buffer solution. However, in this case, the microfluidic device requires a separate device and process to add or eliminate such a pH regulating solution and a sample solution is diluted. The solution injection step and the device can cause serious problems in handling materials in microvolumes and the dilution can cause problems in obtaining and amplifying a desired sample. Furthermore, since the pH regulating solution may act as an inhibitor in the subsequent biological analysis process, the pH regulating solution must be removed after being used.
In an effort to solve such problems, a method of regulating pH using electrolysis has been suggested. For example, a method of lysing cells using a device including a cathode, an anode, and a filter is disclosed in Luke P. Lee et al., Lap on a Chip, 5(2):171-178, “On-chip cell lysis by local hydroxide generation”, 2005. FIG. 1 is a schematic view for explaining a conventional method of lysing cells using an electrolysis device including a filter. Referring to FIG. 1, the conventional electrolysis device includes a cathode chamber 11, an anode chamber 12, and a filter 13 interposed between the cathode chamber 11 and the anode chamber 12. Hydroxyl ions OH− are generated in the cathode 11 to increase pH, and hydrogen ions H+ are generated in the anode 12 to decrease pH. Cells 16 are continuously introduced through an inlet 14 into the cathode chamber 11 to be caught by the filter 13. At this time, if electric power is supplied to the filter 13, the cells are lysed due to the increased pH, and DNA passes through the filter 13 and then the anode 12 to be discharged through an outlet 15 to a next chamber. However, since the hydroxyl ions OH− generated in the cathode chamber 11 continuously flow through the filter 13, a sufficiently high pH to achieve cell lysis cannot be maintained. Even though cell lysis occurs, separated DNA may adhere to the anode chamber 12, and thus may not advance to the next chamber.
There is another method of regulating pH using an electrolysis device including an anode chamber, a cathode chamber, and a separating membrane installed between the anode chamber and the cathode chamber. However, since the separating membrane is too thin, it is technically difficult to manufacture a microfluidic device suitable for LOCs.